LUDINGTON, Mich. (WZZM) -- Ludington Police are enlisting the help of botanists and local plant hobbyists in the search for Baby Kate. Investigators have identified 10 plants they believe will help them get one step closer to finding Katherine Phillips.

Baby Kate was four months old when she disappeared in June 2011. Her biological father, Sean Phillips, is currently in prison, convicted of unlawful imprisonment in the case. In a letter from behind bars, Phillips said he put Katherine in a "peaceful place."

In June 2011, police found small clumps of soil on Phillips shoes. Botanists from the University of Michigan and Michigan State University have found traces of plants in the soil samples; some are common like pine and cedar, but investigators are especially interested in an extremely rare variety of sedge: Carex atlantica, also known as prickly bog sedge.

"This is kind of a botanical fingerprint that we are looking at," said Dr. Frank Telewski, a biologist at MSU.

Ludington Police Chief Mark Barnett is now asking for 100 volunteers to form a botanical search team to find the plant. "When you have information that leads to a step forward you are excited about it."

The search will take place June 28-29, exactly two years after Baby Kate disappeared. Police hope the search for the rare variety of sedge will lead to exactly where Sean Phillips was and the discovery of Katherine Phillips' body.

Anyone with experience in identifying local plants and who are interested in helping with the search should fill out an application on the City of Ludington website under Botanical Search Team. The group will search Mason County looking for the plant, which will be producing a small fruit that time of year.

"It is just coincidental that the time of the disappearance that the fruit were ripe and being shed. So that is when it was picked up on the shoes," said Dr. Telewski.

"The significance of this material is it is know within the capability of law enforcement to scientifically determine where Sean Phillips had been walking on the day that baby Kate went missing," said Chief Barnett.

Police have identified likely search locations but would not say if they are areas searched in 2011.